CN111164268B

CN111164268B - Window fastener

Info

Publication number: CN111164268B
Application number: CN201880063424.9A
Authority: CN
Inventors: 布赖斯·艾伦·莫洛伊; 刘易斯·约瑟夫·艾萨克森
Original assignee: Assa Abloy New Zealand Ltd
Current assignee: Assa Abloy New Zealand Ltd
Priority date: 2017-09-28
Filing date: 2018-09-27
Publication date: 2022-11-04
Anticipated expiration: 2038-09-27
Also published as: CA180465S; AU2018341396A1; US20200270917A1; WO2019066661A1; US11661772B2; JP7157147B2; CA3077336A1; NZ762857A; JP2020535337A; CN111164268A

Abstract

A window fastener comprising: a base configured to be connected to a window sash; a handle carrying a latch tongue, the handle pivotally connected to the base between a latched position and an unlatched position; and an interface between the base and the handle, wherein the interface causes the latch tongue to move axially closer to the base when the handle is pivoted from the unlatched position to the latched position; and wherein the interface moves the latch tongue axially away from the base when the handle is pivoted from the latched position to the unlatched position.

Description

Window fastener

Technical Field

The present invention relates to a window fastener.

Background

To latch a suspended window in a closed position, there are typically fasteners operated with one or more handles mounted to the sash. Wedge fasteners are known which have a pivotally movable handle with a tongue which can engage on a wedge element. The fastener will normally be fastened to the sash and the wedge to the frame.

The fastener may include two spaced apart tabs, one tab for securing the window in the closed position and the other tab for securing the window in the ventilation position. These fasteners have the advantage of providing a degree of security against unauthorized access through the window, while also allowing the window to be partially opened to provide airflow into the building.

Another form of window fastener is a "wedge-less fastener" which relies on a movable flap to cover the edge of the window frame when the sash is in the closed position. In many such fasteners, if the handle is not rotated sufficiently to allow the flap to rotate fully horizontally, the lower inner end of the flap cannot pass over the upper outer edge of the bottom side of the frame when the sash is pulled closed and can strike the frame, possibly damaging the frame, sash and fasteners.

Providing a more robust flap or attachment mechanism increases cost and may reduce aesthetics.

The present invention may provide an improved window fastener or at least provide the public or industry with a useful choice.

Disclosure of Invention

According to an exemplary embodiment, there is provided a window fastener including: i. a base configured to be connected to a window sash; a handle carrying a latch tongue, the handle pivotally connected to the base between a latched position and an unlatched position; an interface between the base and the handle, wherein the interface moves the latch tongue axially closer to the base when the handle is pivoted from the unlocked position to the latched position, and wherein the interface moves the latch tongue axially away from the base when the handle is pivoted from the latched position to the unlocked position.

It is acknowledged that the terms 'comprise', 'comprising', and 'containing' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purposes of this specification, unless otherwise indicated, these terms are intended to have an inclusive meaning-i.e. that it may be taken to mean an inclusion of the listed directly referenced components, and possibly also other non-specified components or elements.

The reference to any document in this specification does not constitute an admission that it is prior art, may be effectively combined with other documents or forms part of the common general knowledge.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention, in which:

FIG. 1 is a front perspective view of a fastener;

FIG. 2 is a rear perspective view of the fastener of FIG. 1;

FIG. 3 is an exploded view of the fastener of FIG. 1;

FIG. 4 is a rear perspective view of the handle;

FIG. 5 is a front perspective view of a tongue washer;

FIG. 6 is a rear perspective view of the tongue washer of FIG. 5;

FIG. 7 is a front perspective view of the base;

FIG. 8 is a rear perspective view of the base of FIG. 7;

FIG. 9 is a detailed view of the cam surface of FIG. 8;

FIG. 10 is a perspective view of the rear gasket;

FIG. 11 is a top perspective view of the venting button;

FIG. 12 is a bottom perspective view of the venting button;

FIG. 13 is a perspective view of a screw;

FIG. 14 is a front view of the fastener in a closed position;

FIG. 15 is a rear view of the fastener in the closed position;

FIG. 16 is a top view of the fastener in a closed position;

FIG. 17 is a side view of the fastener in a closed position;

FIG. 18 is a front view of the fastener in a transitional position;

FIG. 19 is a rear view of the fastener in the transitional position;

FIG. 20 is a top view of the fastener in the transitional position;

FIG. 21 is a side view of the fastener in a transitional position;

FIG. 22 is a front view of the fastener in an open position;

FIG. 23 is a rear view of the fastener in an open position;

FIG. 24 is a top view of the fastener in an open position; and

FIG. 25 is a side view of the fastener in an open position.

Detailed Description

The present application describes a method of securing a window (e.g., a sunroof or a casement window) using a single fastener or multiple fasteners. In a general sense, the embodiments provide a fastener configured such that rotation of the handle 1 causes rotation and axial movement of the latch tongue. When the fastener is rotated to the closed position, the latch tongue is pressed toward the window frame, and when the fastener is rotated to the open position, the latch tongue is released from the window frame.

Fig. 1 is a front perspective view of the fastener, and fig. 2 is a rear perspective view of the fastener of fig. 1. The fastener comprises a base 5 fixed to the window frame and a handle 1 for operating the fastener. The latching tongue 3 and the venting tongue 2 (if present) are carried by the handle 1. The latch tongue 3 and the ventilation tongue 2 (if present) are configured with wear surfaces to prevent window frame damage (as will be described in more detail below).

Fig. 3 is an exploded view of the fastener of fig. 1. The base 5 includes a rear surface configured to interface with the rear gasket 7 and a front surface to interface with the tongue gasket 6. The tongue washer 6 includes an inner surface configured to interface with surfaces on the latch tongue 3 and the boss 10. The boss 10 protrudes from the handle 1 and is rotationally aligned with the handle 1, the tongue washer 6 and the rear washer 7. The cover 4 can accommodate a base 5. The screw 9 may be fixed into the handle 1 from the rear of the fastener.

Handle 1

Fig. 4 is a rear perspective view of the handle 1. The handle 1 provides an ergonomic lever to grip and leverage the mechanism. One end of the handle 1 is fixed to the base 5 of the fastener via a boss 10. In the illustrated embodiment, the boss 10 includes three keyways 11 that are complementary to structures on the tongue washer 6 and the rear washer 7 to rotationally align the handle 1, tongue washer 6 and rear washer 7. Any other suitable key configuration may be used to rotationally align the handle 1, the tongue washer 6 and the rear washer 7. For example, a different number of keyways may be included. Any shape or number of keys capable of transferring a load between the handle and the washer may be used. The keys may be asymmetrically designed in a manner such that the washer can only be attached in one orientation to prevent incorrect assembly of the product. The width of the key grooves 11 may be substantially the same as the width of the space around the boss 10 between the key grooves 11.

The internal bore 13 of the boss 10 provides a means for securing all of the components making up the fastener together via the screw 9 which fits into the bore 13.

The stopper 20 protrudes from the back of the handle 1 below the boss 10. The stop 20 is substantially cubic and may protrude by about 1.3mm. Stop 20 may limit rotation of handle 1 beyond the closed position by interacting with stop 520 or another surface on, for example, base 5.

The handle 1 may be die cast zinc, or any other suitable material including, but not limited to, polymers, aluminum, and other metals.

The latching tongue 3 includes a recess 17 defined by a wall 19 to retain a wear surface 601 integral with the tongue washer 6. In other embodiments, the wear surface may be a separate component from the tongue washer 6, may be integral with the latch tongue of the handle 1, or may be omitted. In the centre of the recess 17 of the latching tongue 3 there is a pillar 16, on which the tongue washer 6 is clamped, so that the tongue washer 6 is held firmly against the handle 1. The washer portion of the tongue washer 6 has an internal profile that is complementary to the profile of the boss 10, as the tongue washer 6 comprises three keys 611 that fit into the keyways 11 of the boss 10. In other embodiments, the washer may comprise a keyway and the boss may comprise a key.

The ventilation tongue 2 comprises a recess 18 and a pillar 15 to hold the ventilation button 12, which serves as a wear surface. The venting button 12 may be omitted. The wear surface may be provided integrally with the ventilation tongue.

Non-ventilated fastener

The embodiment shown depicts a ventilation fastener comprising a second ventilation tongue 2. However, other embodiments may omit the vent flap 2.

Other embodiments may include a high profile version that omits the ventilation flap 2, but has other similar handles. Another embodiment may be a low profile form which also omits the ventilation tongue 2 and the lever section of the handle 1 is closer to the boss 10, thereby providing a solution for mounting where the space for the handle 1 to protrude from the sash is limited.

In further embodiments, the ventilation tongue 2 may protrude from the side of the handle 1 opposite the latching tongue 3. Thus, by rotating the handle 180 degrees from the closed position, the fastener can be moved into the venting configuration.

Tongue washer 6

Fig. 5 is a front perspective view of the tongue washer, and fig. 6 is a rear perspective view of the tongue washer of fig. 5. The tongue washer 6 comprises a set of

surfaces

606, 608, 609 to interact with

corresponding surfaces

506, 508, 509 on the front side of the base 5 to provide axial movement when the handle 1 is turned. Surface 609 is an open bearing surface, surface 606 is an inclined lift surface, and surface 608 is a closed bearing surface.

Surfaces

606, 608, 609 of tongue washer 6 may act as cam followers on

surfaces

506, 508, 509. The tongue washer 6 is rotationally locked to the handle 1 by the same key as the rear washer 7. The tongue washer 6 also comprises a bridging web 620 connecting the washer portion of the tongue washer 6 to the wear surface 601. When the window is closed, the wear surface 601 presses against the window frame. The tongue wear surface is contained within a locating recess 17 in the handle 1.

Tongue washer 6 may be made of any suitable material, such as plastic. The material is preferably resistant to wear but not to wear on the window frame. For example, a softer material may be selected than the surface treatment of the window frame. The material preferably has high ultraviolet stability and heat resistance. In some cases, the wear surface may be a thermoelastic polyester elastomer.

Combining the tab washer 6 with the wear surface 601 facilitates assembly as it reduces the number of parts that must be handled to bring the entire fastener together. In other embodiments, wear surface 601 may be a separate component or button from tongue washer 6.

While it is possible to omit the tongue washer 6 and instead have the boss 10 shaped to have surfaces that interface with the seat 5 (e.g., surfaces similar to those of

surfaces

606, 608, 609), this can increase the wear rate as the abrasive materials will bear against each other. For example, the zinc bosses on the zinc base may not wear well.

The rear surface of the tongue washer 6 includes a retention cavity 622 molded into the tongue washer 6 behind the wear surface 601. The retaining cavity 622 retains the post 16 of the handle 1 via an interference fit to securely hold the tongue washer 6 against the handle 1.

When the tongue washer 6 and the handle 1 are coupled, the outer wall 624 of the tongue washer 6 overlaps the wall 19 of the latching tongue 3. Thus, the wall 19 is sandwiched between the outer wall 624 of the tab washer and the outer surface of the retention chamber 622 and may have a snug fit.

This results in a relatively secure coupling between the flap washer 6 and the handle 1. This may also provide improved protection against impact damage to the window frame during improper handling. This may for example avoid that the latch tongue 3 comes into contact with the metal surface of the frame when the handle 1 is rotated towards the closed position before the sash has been fully pulled against the frame.

Base 5

Fig. 7 is a front perspective view of the base 5, and fig. 8 is a rear perspective view of the base of fig. 7.

The front of base 5 includes a set of

surfaces

506, 508, 509 on the front of base 5 to interface with

surfaces

606, 608, 609 of tongue washer 6. The

surfaces

506, 508, 509 act as cam surfaces in that they convert rotational movement of the handle 1 into axial movement, thereby moving the handle axially towards or away from the base 5, depending on the direction of rotation. Surface 509 is an open bearing surface, surface 506 is an inclined lifting surface, and surface 508 is a closed bearing surface. The set of surfaces are separated at three stops 510.

The inclusion of three sets of surfaces and stops provides stability to the handle. Including two or fewer sets of surfaces may create a pivot in the handle and thus create instability. This will result in additional wear of the rounded bearing surface as it will have to support the joint more. Over time, these may wear and the joint may become loose.

It is possible to include more than three sets of surfaces, but limited by the operating angle. In an embodiment with a 90 operating angle, the 360 boss is then divided into 90, providing the theoretical possibility of four sets of surfaces and stops. The three sets of surfaces and stops provide suitable dimensions for carrying the load, providing support and inherent stability. In other embodiments with a reduced opening angle, a greater number of cams or ramps may be included.

The base 5 may be die cast zinc or made of any other suitable metal. It may be made of plastic, providing adequate strength and wear requirements.

The height difference between the closed bearing surface and the open bearing surface on the tongue washer 6, the rear washer 7 and the base 5 is matched (since the profile is repeated on all three parts), which in the embodiment shown is about 2.5mm. The height difference may be smaller or larger if the profile of the cam or ramp is adjusted.

Similarly, the slope of the ramp matches the profile of the tongue washer 6, the rear washer 7 and the base 5. In the embodiment shown, a height variation of 2.5mm is provided over a 45 ° rotational movement of the handle 1. The slope of the ramp may be constant or may vary (e.g., start gradually and then increase once the handle begins to move).

The thickness of the cam surface may be between 1.8mm and 1.9 mm. This may vary if the overall product is larger or smaller.

Stops 520 protrude from the front of the base 5 below the

surfaces

506, 508, 509. The stopper 520 is substantially cubic and may protrude from the front of the base 5 by about 1.3mm. The stop 520 may limit rotation of the handle 1 beyond the closed position by interacting with another surface, such as the rear surface 21 of the handle 1. This prevents further rotation of the handle 1 beyond the closed position which could otherwise damage the fasteners. In this way, the stopper 520 functions as a stopper. Both the stop 520 and the stop 20 may be made of a relatively strong material, such as metal, making it difficult or impossible for a user to manually force the handle 1 to rotate beyond the closed position.

The rear of the base 5 includes corresponding

surfaces

506, 508, 509 that interface with

surfaces

706, 708, 709 on the rear gasket 7. Surface 709 is an open support surface, surface 708 is a closed support surface, and surface 706 is an inclined lifting surface.

Surfaces

706, 708, 709 of rear washer 7 may act as cam followers on

surfaces

506, 508, 509.

The features on the back side of the base 5 are rotationally offset from the features on the front side. Fig. 9 shows a detailed view of the

surfaces

506, 508, 509 of fig. 8. Stop surface 510A is rotationally offset from stop surface 510B. This ensures that the base 5 is sufficiently thick and robust in all areas. This is an example of how the front and rear surfaces are rotationally offset to avoid weak points.

The rear of the base 5 may include an alignment recess 530 configured to mate with an alignment pin 730 protruding from the side of the rear gasket 7. Alignment recess 530 and alignment pin 730 each have a generally circular cross-section. The alignment recess 530 and the alignment pin 730 may help align the rear gasket 7 with the base 5 during assembly. Additionally, there may be multiple sets of mating recesses 530 and pins 730.

The central boss 504 of the base 5 between the retention ledges 512 is thicker to accommodate the rear gasket 7. The base 5 includes a pair of countersunk holes 502 to secure the fasteners to the sash. The retention ledge 512 retains the cover 4, which conceals the set screw. The thickness of the base 5 at the location of the set screws remains relatively thin (and may be as thin as possible) while still maintaining sufficient strength in the component (and preferably as strong as possible). This may be indicated by regulatory standards for handle forces used to operate windows. In some embodiments, the handle force for operating the window is less than 90N to initiate and maintain movement of the protruding sash. The minimum base thickness at the position of the set screw allows the latching tongue 3 to move away from the base 5 and the cover 4 when the latching tongue 3 is rotated and moved axially.

Spring

In some embodiments, a spring may be provided to act on the rear washer 7 to hold the fastener in either the open or closed position. This may be in the form of a moulded plastic leaf spring, for example, with a pre-load acting on the rear washer 7. The spring may comprise one or more legs to locate and retain in the base 5 via a press fit. Alternative methods of securing the spring to the base 5 may also be used, such as swaging or riveting the base to retain the spring. The stop projection of the spring can act on the outer surface of the rear gasket 7 so as to be placed in two stop positions of the rear gasket 7. This can provide a positive feel to the handle when the handle 1 reaches either of the two positions at each end of the handle stroke, thereby holding the handle 1 in either the open or closed position.

The spring may be made of any suitable material, such as plastic, which provides good performance in terms of wear and retained resilience to provide an effective stop throughout the life of the product.

Alternatively, the preloading of the rear washer 7 may be achieved by a combination of helical spring ball bearings or various other resilient members.

Rear gasket 7

Fig. 10 is a perspective view of the rear gasket 7. The rear washer 7 comprises a central boss 712 comprising a key 711 which locks the rotation of the rear washer 7 to the handle 1. Beyond the boss 712, there is a flange 713 and a stop 710 having

surfaces

706, 708 and 709 that serve as bearing surfaces and lifting profiles. These surfaces were patterned three times around the gasket.

The rear gasket 7 may be of any suitable material (e.g. zinc or plastic).

The rear washer 7 allows the screw to join all of the elements of the joint together by providing the front washer with a complementary cam or inclined lifting surface to allow the handle to rotate through its full movement.

The front and rear washers have the same surface profile as they are subjected to the same rotational and axial movements and are secured together by screws.

The rear washer may include an alignment pin 730 configured to mate with an alignment recess 530 disposed in the rear of the base 5. Alignment recess 530 and alignment pin 730 both have a substantially circular cross-section. The alignment recess 530 and the alignment pin 730 may help align the rear gasket 7 with the base 5 during manufacturing. Additionally, there may be multiple sets of mating recesses 530 and pins 730.

Ventilation button 12

Fig. 11 is a top perspective view of the venting button 12, and fig. 12 is a bottom perspective view of the venting button 12. Venting button 12 performs a similar function as wear surface 601 on tongue washer 6. However, since the venting button 12 is not compressed against the frame, there is less wear requirement. The venting button 12 prevents the handle 1, in particular the venting tongue 2, from scraping the surface treatment of the window frame when the handle 1 is in the venting position. The engagement surface 1201 of the venting button 12 is formed of a suitable material to avoid damaging the surface finish of the window frame. For example, a relatively soft plastic may be used. The venting button 12 is held on the post 15 on the venting tongue 2 of the handle 1 by the holding finger 1202.

Screw 9

Fig. 13 is a perspective view of the screw 9. Screws 9 may secure the various components into the assembled mechanism. The screw 9 in the embodiment shown is a delta screw 9 to be secured into the handle 1 from the rear of the fastener. This function can also be achieved by a riveting process.

An extended lip 904 on the head of the screw 9 allows a greater surface area to apply pressure to hold all components together in the functional assembly.

Frictional force

In some embodiments, the assembly may be configured to have sufficient friction such that the handle 1 tends to remain in place unless manipulated by the user. For example, when the user places the handle 1 in a partially open position (e.g., 45 degrees from a fully closed position), the frictional force is high enough that the assembly can hold the weight of the handle 1 in place until the user further engages the handle 1. For example, the assembly may be configured such that between about 2.5Nm and about 5Nm of torque may be required to move the handle 1.

This may be achieved by forming one or both of the tongue washer 6 and the rear washer 7 from a material having suitable friction compared to the base 5. In addition, the wear resistant material may be selected such that the assembly maintains sufficient friction throughout its life.

Operation of

Other mechanisms for converting rotational motion to axial motion may be provided. For example, a thread may be provided to convert a rotational movement of the handle 1 into an axial movement of the latch tongue 3 towards and/or away from the flap. The base 5 may include a threaded hole and the handle 1 may include a threaded boss that screws into the threaded hole of the base.

In the illustrated embodiment, the conversion of the rotational movement of the handle to axial movement is achieved using two pairs of sets of ramped lift surfaces or cams, a first set of ramped

lift surfaces

506 and 606 being provided on the front side of the base 5 and on the tongue washer 6. The base 5 remains stationary when the rotation of the tongue washer 6 and the rear washer 7 is keyed to the handle 1. A second set of inclined lifting surfaces 506 and 706 are on the rear gasket 7 and on the rear side of the base 5.

In the embodiment shown, the radial movement of the handle 1 of the fastener from the closed extreme to the open extreme is 0 ° to 90 °. In other embodiments, the range of radial movement of the handle 1 may be between 0 ° and 180 °.

Fig. 14-17 are front, rear, top and side views, respectively, of the fastener in a closed position. The stop 610 of the tongue washer abuts the stop 510 of the base and the protruding surface 609 of the tongue washer is positioned adjacent to the surface 508 of the base 5. Thus, there is maximum overlap between the tongue washer 6 and the base 5, and therefore the handle 1 and the latch tongue 3 are maximally close to the base 5. When the fastener is in the closed position, the wear surface 601 of the tongue washer 6 presses against the window frame, compressing the window seal when the window is closed. The compression window seal prevents water and air from entering.

Fig. 18-21 are front, rear, top and side views, respectively, of the fastener in the transitional position.

Starting from the closed position, the first 45 ° movement is radial and axial due to the inclined lifting surface features of the seat 5 and of the tongue and rear gasket 7. The angled lifting surface 606 of the tongue washer 6 and the angled lifting surface 706 of the rear washer 7 slide up the angled lifting surface 506 of the base 5, reducing compression of the window frame by increasing the distance between the tongue washer 6 and the base 5.

During the first 45 ° of opening, the worn part of the latching tongue 3 rotates through an arc of a circle. The latch tongue 3 remains in contact with the window frame, however, the pressure on the window seal is released due to the axial movement in the joint during this time period. When the handle 1 has been rotated through the entire 45 deg., the movement is only converted into a rotational movement. At this point, there is no pressure between the latch tongue 3 and the window frame, since the axial movement is greater than the window seal compression distance. The remaining 45 ° of the opening arc of the handle 1 is then a pure rotational movement without further axial change, as the open bearing surface 609 of the tongue washer 6 and the open bearing surface 709 of the rear washer 7 slide on the open bearing surface 509 of the base 5.

Fig. 22-25 are front, rear, top and side views, respectively, of the fastener in an open position. In order to close the fastener, the handle 1 must be rotated in a direction opposite to the opening movement. During the first 45 ° of closure, the handle 1 is moved fully rotationally as the open bearing surface 609 of the tongue washer 6 and the open bearing surface 709 of the rear washer slide over the open bearing surface 509 of the base 5. The last 45 of the movement is radial and axial due to the cam features of the base 5, the tongue washer 6 and the rear washer 7. The inclined lifting surfaces 606 of the tongue washer 6 and the inclined lifting surfaces 706 of the rear washer 7 slide down the inclined lifting surfaces 506 of the base 5, thereby increasing the overlap area between the tongue washer 6 and the base 5.

In this embodiment, the ratio of axial and rotational motion to pure rotational motion is 1:1 (i.e., half the stroke is pure rotational). However, in other embodiments, the ratio of axial and rotational movement to pure rotational movement may vary. Any proportion or ratio of rotational movement may also include axial movement as long as the tongue is able to clear the base 5 and cover 4.

By hand

The embodiments describe a right hand component. A left-hand component may be provided that is a mirror image version of the right-hand component. Features may be added or omitted to the left-hand component to prevent production of a misassembled product using a mixture of left-hand and right-hand components. For assembly purposes, the left and right hand washers and bosses may have different key configurations to prevent incorrect assembly.

Assembling method

To assemble the fastener, the components may be stacked "upside down" on the handle. First, the tongue washer 6, the rear washer 7 and the base 5 can be fitted to the boss 10 in the correct orientation. The screw is driven through the stack into the handle to create the final joint. The venting button 12 (when present) may be added in a separate operation.

Manufacturing method

The parts may be zinc die cast, moulded in plastic or manufactured from the corresponding material by any other suitable method.

In the case of zinc parts, if the zinc part is not visible in the finished product, it may be subjected to a corrosion-protection pretreatment, or the visible part may be subjected to powder coating or decorative plating. In the case where the rear gasket 7 is zinc, the rear gasket 7 may be plated for wear resistance.

While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.

Claims

1. A window fastener comprising:

i. a base configured for connection to a window sash;

a handle carrying a latch tongue, the handle pivotally connected to the base to pivot about an axis between a latched position and an unlatched position;

an interface between the base and the handle; and

a washer located between the base and the handle,

wherein the interface moves the latch tongue axially relative to the axis proximate the base when the handle is pivoted from the unlocked position to the latched position; and is

Wherein the interface moves the latch tab axially away from the base relative to the axis when the handle is pivoted from the latched position to the unlatched position;

wherein the interface comprises a cam surface;

wherein the cam surface is a surface of the base; and is

Wherein the washer is rotationally aligned with the handle and has a complementary surface to the cam surface of the base such that, in use, the washer overlaps the base when the fastener is in a latched position,

wherein the cam surface comprises at least a closed bearing surface, a lifting surface and an open bearing surface,

wherein the window fastener further comprises a rear washer positioned behind the cam surface of the base and rotationally aligned with the handle.

2. The window fastener of claim 1, wherein the base includes an aperture through which the handle pivots.

3. The window fastener of claim 1 or 2, wherein the complementary surface acts as a cam follower on the cam surface when the handle is pivoted.

4. The window fastener of claim 1 or 2, wherein the complementary surface is substantially concentric with the cam surface.

5. The window fastener of claim 4, wherein the washer is integral with a wear surface for the latch tab.

6. The window fastener of claim 1 or 2, wherein the washer includes a wall configured to overlap the latch tab.

7. The window fastener of claim 1 or 2, wherein the cam surface is substantially circular.

8. The window fastener of claim 1, wherein the cam surface includes three sets of closed bearing surfaces, raised surfaces, and open bearing surfaces.

9. The window fastener as recited in claim 2, wherein a keyed boss through the aperture rotationally aligns the rear washer with the handle.

10. The window fastener of claim 9, wherein the rear surface of the base includes a cam surface configured to interface with a follower cam surface of the rear washer.

11. A window fastener according to claim 1 or claim 2, wherein the handle further comprises a vent tab which is engageable with a window frame in use to hold the window half-open when the handle is in a vent position.

12. The window fastener of claim 1 or 2, comprising a spring configured to bias the handle to be positively positioned to at least the unlocked position.

13. The window fastener as recited in claim 12, wherein the spring is configured to bias the handle to positively locate the latched and unlatched positions.

14. The window fastener of claim 1 or 2, wherein the interface comprises threads.

15. The window fastener of claim 1 or 2, wherein the base includes a base stop and the handle includes a handle stop, the base stop and the handle stop configured to prevent the handle from pivoting beyond the latched position.